I think I'm right in saying that there's a time limit after which you can't edit your posts any more (perhaps a week?). This makes sense up to a point, but it causes a bit of a problem when you have a problem that slowly develops: this thread doesn't really bear any resemblance to the title I gave it when it started, but because that was 4 weeks ago I can't edit the original post. And as far as I know, editing the first post is the only way to edit the title.
I suspect that this may be a problem for several people, which is a pain because there may well be people who would be able to solve a particular thread, but don't look at it because the title suggests its got nothing to do with their area of expertise... The only way round it that I can see would be to start a new thread, which is of course very messy and A Bad Thing. Any ideas?